Abstract:

The present invention relates to a method for crystallization of
(2R)-2-{(3S,
4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidin-4-yl}propi-
onic acid, and is characterized in that crystallization is carried out by
mixing a solution containing the compound with a substituted aromatic
hydrocarbon solvent and/or a halogenated hydrocarbon solvent. The method
can provide a crystal of the compound with a high purity and a high yield
while the content of 2S isomer is kept at a low level.

Claims:

1. A method for producing a compound represented by the formula (1),
comprising a step of mixing a solution of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid represented by the following formula (1):
##STR00010## with a substituted aromatic hydrocarbon solvent and/or a
halogenated hydrocarbon solvent for crystallization.

2. The production method according to claim 1, wherein concentration is
carried out during and/or after mixing the solution of the compound
represented by the formula (1) with the substituted aromatic hydrocarbon
solvent and/or the halogenated hydrocarbon solvent.

3. The production method according to claim 1, wherein a ratio of a total
weight of the substituted aromatic hydrocarbon solvent and the
halogenated hydrocarbon solvent is 1/2 or higher in solvents contained in
a crystallization mother liquid.

4. The production method according to claim 1, wherein a temperature of a
mixed solution is 50.degree. C. or lower when the crystallization is
carried out.

5. The production method according to claim 1, wherein a mixed solution is
stirred at a stirring intensity of 10 W/m3 or higher when the
crystallization is carried out.

6. The production method according to claim 1, wherein the solution of the
compound represented by the formula (1) contains esters or ketones.

7. The production method according to claim 1, wherein the solution of the
compound represented by the formula (1) contains water.

8. The production method according to claim 1, wherein the solution of the
compound represented by the formula (1) has a concentration of the
compound represented by the formula (1) of 1% by weight or higher.

9. The production method according to claim 1, wherein the halogenated
hydrocarbon solvent is chain halogenated hydrocarbons.

10. (2R)-2-{(3S,4S)-3-[(1R)-1-(tert-Butyldimethylsilyloxy)ethyl]-2-oxoazet-
idin-4-yl}propionic acid represented by the general formula (1),wherein a
content of (2S)-2-{(3S,4S)-3-[(1R)-1-(tert-butyl
dimethylsilyloxy)ethyl]-2-oxoazetidin-4-yl}propionic acid represented by
the following formula (2): ##STR00011## is 1% or less.

12. The crystal of (2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethyl
silyloxy)ethyl]-2-oxoazetidin-4-yl}propionic acid represented by the
formula (1) according to claim 11, wherein a content of
(2S)-2-{(3S,45)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid represented by the formula (2) is 1% or less.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an improved method for
crystallization of azetidinonecarboxylic acid useful as a synthesis
intermediate of a 1β-methylcarbapenem derivative having an
antibacterial activity.

BACKGROUND ART

[0002]A 1β-methylcarbapenem derivative has an excellent antibacterial
activity to pathogenic bacteria in a wide range including gram positive
and gram negative microorganism; has particularly strong antibacterial
activity even to cephem-resistant bacteria; and is excellent in stability
in a living body. Therefore, the derivative has drawn attention as an
antibacterial agent.

[0003]Such a 1β-methylcarbapenem derivative is synthesized by various
methods. Azetidinonecarboxylic acid represented by the following formula
(1):

##STR00001##

is known as useful synthesis intermediate for the derivative, and many
synthesis methods thereof are disclosed. In a synthesis method of the
compound represented by the formula (1) (hereinafter, sometimes referred
to as a "compound (1)"), the following methods are known as a method of
obtaining crystal thereof:

[0004]A) a method of carrying out crystallization in water to obtain the
crystal by acidifying an aqueous alkaline solution of the compound (1)
with an aqueous hydrochloric acid solution (Patent Documents 1 and 2);

[0005]B) a method of acidifying an aqueous alkaline solution of the
compound (1) with an aqueous hydrochloric acid solution; carrying out
extraction with ethyl acetate; thereafter obtaining a crystalline solid
substance by distillation of an ethyl acetate solution of the compound
(1), which is obtained by drying with magnesium sulfate and filtration,
under reduced pressure; and washing the solid substance with hexane to
obtain the crystal (Patent Document 3);

[0006]C) a method of acidifying an aqueous alkaline solution of the
compound (1) with an aqueous hydrochloric acid solution; carrying out
extraction with ethyl acetate; concentrating the ethyl acetate solution
of the compound (1), which is obtained by drying with magnesium sulfate
and filtration, under reduced pressure; crystallizing from the residue by
using an ethyl acetate and hexane solvent to obtain the crystal (Patent
Document 4); and

[0007]D) a method extracting the compound (1) obtained by synthesis
reaction with ethyl acetate, dissolving again the residue obtained by
drying and concentration process in ethyl acetate, removing insoluble
matter by filtration, concentrating the filtrate to obtain a crystalline
solid, and re-crystallizing the solid from a mixed solvent of ethyl
acetate and benzene to obtain the crystal (Patent Document 5).

[0008]However, the methods of obtaining the crystal have the following
problems in term of a crystal recovery yield and a crystal purity of the
compound (1):

[0009]low purity by the methods A) to C) and

[0010]low yield by the method D).

[0011]All of the above-mentioned methods have problems and thus are not
satisfactory as a production method of the compound (1).

[0012]Further, as a result of studies by the inventors of the present
invention, it was found that the above-mentioned methods A) to C) are
inferior in the removal effect of a compound represented by the following
formula (2) (hereinafter, sometimes referred to as "2S isomer"):

##STR00002##

as a byproduct of the processes. In the synthesis of a precursor needed to
produce the compound (1), investigations and researches relevant to a
method of controlling byproduct production of a compound to be a
precursor of the 2S isomer are positively carried out. The fact can be
understood from Patent Documents 2 and 4. The methods A) to C) inferior
in the 2S isomer removal effect are insufficient as a method for
producing the compound (1) which is an intermediate of a pharmaceutical
agent, since suppression of the content of the 2S isomer contained the
crystal of the compound (I) are very critical issue.

[0013]Furthermore, the above-mentioned methods B) to D) are not
satisfactory as a production method of the compound (1), since the
methods involve a large number of complicated and non-economical
operations from a viewpoint of industrial production scale. The operation
is exemplified by drying of the ethyl acetate solution obtained with
extraction of the compound (1) by using magnesium sulfate or the like and
following filtration needed after the drying, recrystallization of the
crystalline solid obtained by repeating concentration and dissolution,
and the like.

[0014]Patent Document 1: JP 7-25848 A

[0015]Patent Document 2: JP 2000-44538 A

[0016]Patent Document 3: JP 5-105660 A

[0017]Patent Document 4: WO 2002/012230

[0018]Patent Document 5: JP 4-368365 A

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

[0019]As described above, the conventional methods of obtaining the
crystal have the above-mentioned problems in terms of a crystal
production yield or a crystal purity, and are not satisfactory as the
production method of the compound (1), since the methods are inferior in
the effect of removing 2S isomer represented by the formula (2), and
involve a large number of complicated and non-economical operations in
consideration of industrial scale production.

[0020]An objective to be achieved by the present invention is to provide
an improved method of crystallization to obtain a crystal of the compound
(1) with a high yield and a high purity.

Means for Solving the Problems

[0021]The present inventors made intensive studies on the method of
crystallization of the compound (1). As a result, the inventors found
that the compound represented by the formula (2) can be efficiently
removed and a crystal of the compound (1) can be obtained with a high
yield and a high purity by mixing a solution containing the compound (1)
with a substituted aromatic hydrocarbon solvent and/or a halogenated
hydrocarbon solvent and carrying out crystallization; and accordingly the
finding leads to completion of the present invention.

[0022]The present invention relates to a method for producing a compound
represented by the formula (1), characterized in comprising a step of
mixing a solution of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid represented by the formula (1):

##STR00003##

with a substituted aromatic hydrocarbon solvent and/or a halogenated
hydrocarbon solvent for crystallization.

[0023]Further, the present invention relates to
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid represented by the general formula (1), wherein a
content of (2S)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyl
oxy)ethyl]-2-oxoazetidin-4-yl}propionic acid represented by the formula
(2):

[0025]The present invention provides an improved method of crystallization
of the compound (1) useful as a synthesis intermediate of a
1β-methylcarbapenem derivative, and the intermediate with high
purity, and a crystal of the intermediate.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026]Hereinafter, the present invention is described in detail.

[0027]The present invention is characterized in comprising a step of
mixing a solution of (2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyl
dimethylsilyloxy)ethyl]-2-oxoazetidin-4-yl}propionic acid represented by
the formula (1):

##STR00005##

with a substituted aromatic hydrocarbon solvent and/or a halogenated
hydrocarbon solvent for crystallization.

[0028]At first, a solution in which the compound (1) is dissolved is
described.

[0029]A solution in which the compound (1) is dissolved is a solution
containing the compound (1) partially or completely dissolved in a good
solvent described below (hereinafter, sometimes abbreviated as "good
solvent solution of the compound (1)"). A good solvent is a solvent
having high solubility of the compound (1), and is described below with a
specific example.

[0031]Among the above solvents, ethers, esters, ketones and alcohols are
preferable, and esters and ketones are more preferable. As esters, acetic
acid esters such as methyl acetate, ethyl acetate, n-propyl acetate,
isopropyl acetate, n-butyl acetate, sec-butyl acetate, isobutyl acetate,
tert-butyl acetate and the solvent mixtures thereof are preferable, and
ethyl acetate is particularly preferable. As ketones, ketones having 1 to
5 carbon atoms such as acetone, 2-butanone, 3-methyl-2-butanone,
2-pentanone, 3-pentanone, and the solvent mixtures thereof are
preferable, and acetone and 2-butanone are particularly preferable.

[0032]A good solvent solution of the compound (1) may be a crude reaction
solution in which the compound (1) is synthesized by a conventionally
known method and a good solvent is contained, or a solution obtained by
dissolving the compound (1), which is once isolated, in a good solvent.
Further, the solution may be a solution obtained by subjecting a crude
reaction solution of the compound (1) to post-treatment such as washing
with water optionally containing an acid, a base, a salt or the like,
concentration adjustment by condensation, insoluble matter filtration
treatment, and adsorption treatment with activated carbon, based on the
necessity. Further, the solution may be a homogenous or nonhomogenous
solution obtained by concentrating the crude reaction solution in which
the compound (1) is synthesized or the good solvent solution containing
the compound (1) dissolved therein, or furthermore may be a slurry
obtained by carrying out concentration to partially precipitate the
compound (1). No need to say, another solvent other than the good solvent
may exist to an extent that no bad effect is caused. For example, it is
effective and particularly preferable for production in industrial scale
to mix water with the good solvent solution of the compound (1) to give a
water-containing solution, since a solubility of the compound (1) in the
good solvent solution can be improved and a concentration of the compound
(1) in the solution can be increased to reduce a volume of the good
solvent solution.

[0033]A concentration of the compound (1) in a good solvent solution is
not particularly limited; however is generally preferably 1% by weight or
higher, more preferably 3% by weight or higher, and even more preferably
5% by weight or higher, in consideration of a productivity or the like.
Further, an upper limit of the concentration of the compound (1) in the
good solvent solution is preferably equal to or lower than a saturated
solubility of the compound (1) in a good solvent to be used; however the
solution may be supersaturated or may be a slurry by partial
precipitation.

[0034]Next, a substituted aromatic hydrocarbon solvent and a halogenated
hydrocarbon solvent to be used in the present invention is described.

[0035]In the present invention, a substituted aromatic hydrocarbon solvent
and/or a halogenated hydrocarbon solvent are used as a poor solvent.
Hereinafter, the substituted aromatic hydrocarbon solvents and the
halogenated hydrocarbon solvents may be collectively called as "a poor
solvent" in some cases. The poor solvent means a solvent having a low
solubility of the compound (1). It is not common to use the substituted
aromatic hydrocarbon solvent and the halogenated hydrocarbon solvent as a
poor solvent at a time of crystallizing a common organic compound, since
the solvents have a property of well dissolving an organic compound. Even
if the solvents can be used as a poor solvent, it is not common to use
the substituted aromatic hydrocarbon solvent and the halogenated
hydrocarbon solvent as a poor solvent, since the solvents more easily
dissolve an organic compound than aliphatic hydrocarbons such as hexane
often used as a poor solvent and tend to cause undesirable consequence
such as low recovery ratio by crystallization. The present invention is
completed on the basis of a finding that the compound (1) with a high
yield and a high purity can be obtained by using the substituted aromatic
hydrocarbon solvent and/or the halogenated hydrocarbon solvent as a poor
solvent in the crystallization of the compound (1). Such a finding is
significantly remarkable.

[0036]A substituted aromatic hydrocarbon solvent is not particularly
limited as long as the solvent is a poor solvent of the compound (1);
however includes aromatic hydrocarbons having one or more substituents
such as alkyl groups having 1 to 4 carbon atoms, halogens, nitro groups,
and solvent mixtures thereof. Naturally, in case that there are two or
more substituent groups, ortho-, meta- and para-position isomers may be
included. The example of alkyl groups having 1 to 4 carbon atoms includes
methyl, ethyl, n-propyl, isopropyl and the like. The example of halogens
includes fluorine, chlorine, bromine and iodine. Among the examples,
aromatic hydrocarbons having one or more substituents of methyl group and
chlorine and the solvent mixtures thereof are preferable; toluene,
o-xylene, m-xylene and p-xylene are more preferable; and toluene is
particularly preferable.

[0037]The above halogenated hydrocarbon solvents are not particularly
limited as long as the solvents are a poor solvent of the compound (1);
and include chain halogenated hydrocarbon solvents such as
dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane,
1,1,1-trichloroethane and the like. Among the example, dichloromethane is
preferable.

[0038]The above substituted aromatic hydrocarbon solvents and halogenated
hydrocarbon solvents may be singly used respectively, or the combination
thereof may be used.

[0039]Next, a method of crystallization of the compound (1) of the present
invention is described.

[0040]In the present invention, crystallization is carried out by a method
of mixing a good solvent solution of the compound (1) and a poor solvent.

[0041]When crystallization is carried out, a poor solvent may be added to
a good solvent solution of the compound (1) or a good solvent solution of
the compound (1) may be added to a poor solvent. In the case of adding
the poor solvent to the good solvent solution of the compound (1), the
addition may be carried out at once or stepwise. In the case of adding
the good solvent solution of compound (1) to the poor solvent, the
addition may be also carried out at once or stepwise. In the case of the
stepwise addition, the solvent may be added continuously or the solvent
is divided into several portions and the portions may successively be
added. Further, at the time of mixing the good solvent solution of
compound (1) and the poor solvent, the solution and the solvent may be
simultaneously added to be mixed.

[0042]Before mixing a good solvent solution of the compound (1) and a poor
solvent, the good solvent solution of the compound (1) may be subjected
to concentration crystallization or cooling crystallization to
crystallize a portion of the compound (1) and then the poor solvent may
be mixed as described above. The good solvent solution of the compound
(1) formed to be in a slurry state by crystallization and the poor
solvent may be mixed to further accelerate crystallization.

[0043]In addition, a crystallization method by mixing a good solvent
solution of the compound (1) and a poor solvent may also be carried out
properly in combination with concentration crystallization or cooling
crystallization.

[0044]In such a case that a boiling point of a poor solvent is higher than
a boiling point of a good solvent to be used for a good solvent solution
of the compound (1) or a good solvent and a poor solvent are azeotropic,
it is preferable to carry out concentration at the time of mixing the
good solvent solution of the compound (1) and the poor solvent and/or
after mixing the solution and the solvent, since a ratio of the good
solvent in a crystallization solution can efficiently be decreased and a
crystal recovery ratio can be improved. When a ratio of a poor solvent is
higher in a solvent composition before solid-liquid separation operation
described later, the crystal can be obtained at a higher crystal recovery
ratio.

[0045]A method involving a crystallization method of mixing a good solvent
solution of the compound (1) and a poor solvent in combination with a
concentration crystallization and further in combination with cooling
crystallization is particularly preferable, since the method can further
improve a crystal recovery ratio. No need to say, when the concentration
crystallization and the cooling crystallization are carried out, either
one operation may be carried out previously and both operations may be
repeated any times.

[0046]Thus, a crystal with a high purity can be obtained by any
crystallization method described above.

[0047]In the above crystallization operations, a seed crystal may be added
if necessary. A use amount of the seed crystal is not particularly
limited; however, a lower limit is preferably not less than 0.001 w/w
times, more preferably not less than 0.003 w/w times, and particularly
more preferably not less than 0.005 w/w times, respective to the compound
(1) in a good solvent solution. An upper limit of the compound (1) in a
good solvent solution is preferably not more than 0.2 w/w times, more
preferably not more than 0.1 w/w times, and further more preferably not
more than 0.05 w/w times, respective to the compound (1) in a good
solvent solution.

[0048]In the crystallization by mixing a good solvent solution of the
compound (1) and a poor solvent and/or concentration crystallization, a
temperature is not particularly limited; however, the temperature is
preferably 50° C. or lower, more preferably 40° C. or
lower, and particularly more preferably 30° C. or lower, since the
compound (1) is sometimes inferior in a heat stability.

[0049]A use amount of a poor solvent is preferably set every time in
accordance with a crystallization method in order to obtain a desired
crystallization recovery ratio. The amount is not particularly limited;
however, a weight ratio of the poor solvent in a composition of solvent
contained in a mother liquid is generally 1/2 or higher, preferably 2/3
or higher, and more preferably 3/4 or higher. The crystallization mother
liquid means a liquid phase part immediately before a solid-liquid
separation operation described later after a crystallization method of
mixing a good solvent solution of the compound (1) and a poor solvent or
after an operation of concentration crystallization and/or cooling
crystallization to be carried out on the basis of necessity. An formula
for calculating a weight ratio of a poor solvent contained in the mother
liquid is defined as ([weight of poor solvent])/([weight of good
solvent])+[weight of poor solvent]).

[0050]In a crystallization method of mixing a good solvent solution of the
compound (1) and a poor solvent, the poor solvent may be used in a manner
that a weight ratio of the poor solvent can satisfy the above-mentioned
ratio. In case that a crystallization method of mixing a good solvent
solution of the compound (1) and a poor solvent is combined with a
concentration crystallization to be carried out, a mixing of the good
solvent solution of the compound (1) and the poor solvent and
concentration may be carried out in a manner that a weight ratio of the
poor solvent contained in the mother liquid can satisfy the above ratio.

[0051]In the present invention, aging may be carried out at the last of a
crystallization. An aging temperature is not particularly limited;
however, the temperature is preferably as low as possible in terms of
increase of a crystallization recovery ratio and is generally 20°
C. or lower, preferably 10° C. or lower, and more preferably
0° C. or lower. An aging time is not particularly limited;
however, a lower limit is generally 10 minutes or longer, preferably 30
minutes or longer, and more preferably 1 hour or longer. An upper limit
is generally 30 hours or shorter, preferably 20 hours or shorter, and
more preferably 10 hours or shorter, in consideration of a productivity.

[0052]Generally, the above crystallization by mixing a good solvent
solution of the compound (1) and a poor solvent, concentration
crystallization, cooling crystallization and aging are carried out with
stirring. An intensity of the stirring is not particularly limited;
however, the intensity is preferably not lower than 10 w/m3, more
preferably not lower than 50 w/m3, furthermore preferably not lower
than 100 w/m3, and even more preferably not lower than 300
w/m3, as needed motive energy of stirring per unit volume.

[0053]A crystal of the compound (1) obtained by the crystallization method
of the present invention can be isolated by common solid-liquid
separation operation.

[0054]According to the crystallization method of the present invention, it
is possible to obtain the highly pure compound (1) with a high crystal
recovery ratio by executing crystallization in industrially simple
operation such as mixing and concentration of a good solvent solution of
the compound (1) which is obtained by post-treatment such as extraction
operation of a crude reaction solution, without carrying out complicated
operation, which is disclosed as a conventional crystal obtaining method,
such as drying of a solution containing the compound (1) and
recrystallization. The crystallization method of the present invention is
particularly useful at the time of production of the compound (1) in an
industrial scale, since the method is simple in an operation and
economical due to an improvement of a productivity.

[0055]In the case of the methods as the above Patent Documents, a
precursor of a compound represented by the following formula (2):

##STR00006##

which is an isomer of the compound (1), (hereinafter, sometimes referred
to as a "2S isomer") is often produced as a byproduct at the time of
synthesizing a precursor of the compound (1), and the 2S isomer is
contained in a good solvent solution of the compound (1) at the time of
synthesizing the compound (1) from the precursor of the compound (1).
However, the compound (1) can be obtained with high yield and high purity
and the 2S isomer can be effectively removed by the crystallization
method of the invention.

[0056]When the crystallization method of the present invention is
employed, the 2S isomer as an impurity can be removed at 50% or higher of
a removal ratio, preferably 60% or higher, and more preferably 65% or
higher; and thus, the crystallization method of the present invention is
very useful in terms of a remarkable decrease of a content of a 2S isomer
contained in a crystal of the compound (1). The formula for calculating
the removal ratio can be defined as ([content of 2S isomer to compound
(1) in good solvent solution]-[content of 2S isomer in crystal])/[content
of 2S isomer to compound (1) in good solvent solution]×100(%).

[0057]The compound (1) thus obtained in the above-mentioned manner is a
compound with high purity having a content of the 2S isomer as an
impurity of 1% or less, preferably 0.5% or less, and more preferably 0.3%
or less. Since a content of an isomer contained in a
1β-methylcarbapenem antibiotic synthesized as a pharmaceutical agent
from the compound (1) can be decreased by decreasing a content of the 2S
isomer remaining in a crystal, the compound (1) with an extremely small
content of the 2S isomer is very useful.

[0058]The compound (1) obtained by using the present invention is
remarkably useful as a synthesis intermediate for producing a
1β-methylcarbapenem derivative with a high purity.

[0059]The crystal of the compound (1) obtained in the above-mentioned
manner shows main peaks at diffraction angles of, for example,
20=7.48°, 11.30°, 14.50°, 15.04°,
15.54°, 16.54°, 16.94°, 18.58°,
22.68°, 24.24°, 28.50° and 31.62° in a powder
x-ray diffraction obtained by irradiating Kα-beam of Cu, having a
wavelength of λ=1.54 Å. The main peaks are peaks with 10 or
higher relative intensity in case that an intensity of a peak at a
diffraction angle of 2θ=15.04° is defined to be 100. When a
crystal is represented by employing a diffraction angle 2θ in the
present specification, a value of a diffraction angle 2θ is not
limited to values at which the above-mentioned peaks exist and ranges
thereof, and may include a margin of errors. A range within which such
errors are generated can be easily expected by a person skilled in the
art from a measurement condition and the like; and such a range of errors
may be, for example, ±0.05°. The obtained crystal is easily
handled and thus useful.

EXAMPLES

[0060]Hereinafter, the present invention is described much more in detail
with reference to Examples, Comparative Examples and Reference Examples;
however it is not intended that the present invention be limited to the
Examples.

[0062]After
(3S,4R)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1S)-1-methyl-2-p-
ropenyl]azetidin-2-one (10.6 g), acetic acid (17.1 g), ethyl acetate (105
ml) and water (73 ml) were mixed, the mixture was stirred. To the
mixture, potassium permanganate (30.0 g) was added over 1.5 hours while
the reaction solution temperature was kept at 6 to 15° C. Then,
the reaction solution was stirred at 7° C. for 3 hours.
Thereafter, a 27% aqueous solution of sodium hydrogen sulfite (157 ml)
was added while the reaction solution temperature was kept at 6 to
13° C., and the solution was stirred at 7° C. for 30
minutes. Further, 6N HCl was added to adjust pH of the reaction solution
to be at 1.4, and the reaction solution was stirred at 7° C. for
30 minutes. After an organic layer obtained by separating the resulting
reaction solution was washed with water (55 ml) twice, ethyl acetate (28
ml) was added to obtain an ethyl acetate solution (112.5 g) containing
10.2 g of (2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2--
oxoazetidin-4-yl}propionic acid. The solution contained a 2S isomer in an
amount of 2.0% on the basis of the compound (1).

Example 1

[0063]The ethyl acetate solution (40.0 g) of the compound (1) obtained in
Reference Example 1 was concentrated to 10.0 g while the inner
temperature was kept at 24 to 30° C. As a result, a crystal was
precipitated. While the obtained slurry was stirred, toluene (17.8 g) was
added. The slurry was further concentrated to 8.2 g, while the inner
temperature was kept at 21 to 30° C. After toluene (41.9 g) was
added, the slurry was cooled to -20° C. and stirred for 1.5 hours.
It was confirmed that the weight ratio of toluene in the composition of
the solvents at the moment was 1/2 or higher. After the crystal was
separated by filtration, the crystal was washed with toluene (4.2 g). The
obtained wet crystal was dried under reduced pressure at room temperature
for 24 hours to obtain 3.4 g of a dry crystal of the compound (1).

[0064]Crystal purity: 99.0%

[0065]2S Isomer content: 0.7%

[0066]2S Isomer removal ratio: 67%

[0067]Crystal recovery ratio: 92.1%

Comparative Example 1

[0068]The ethyl acetate solution (40.0 g) of the compound (1) obtained in
Reference Example 1 was concentrated to 7.8 g while the inner temperature
was kept at 24 to 30° C. As a result, a crystal was precipitated.
While the obtained slurry was stirred, ethyl acetate (22.8 g) was added.
The slurry was further concentrated to 7.8 g, while the inner temperature
was kept at 27 to 30° C. After ethyl acetate (10.6 g) was added,
the obtained slurry was cooled to -50° C. and stirred for 1.5
hours. After the crystal was separated by filtration, the crystal was
washed with ethyl acetate (3.6 g), and the obtained wet crystal was dried
under reduced pressure at room temperature for 27 hours to obtain 3.2 g
of a dry crystal of the compound (1).

[0074]After zinc metal (6.8 g) of which surface was treated with diluted
hydrochloric acid and
3-(2-bromopropanoyl)-spiro[3-azachloman-2,1'-cyclohexan]-4-one (1.8 g)
were added to dry tetrahydrofuran (60 ml), the mixture was stirred at
25° C. for 1.7 hours. After a solution obtained by dissolving
3-(2-bromopropanoyl)-spiro[3-azachloman-2,1'-cyclohexan]-4-one (16.5 g)
and (3R,4R)-4-acetoxy-3-[(1R)-1-tert-butyldimethylsilyl
oxy]-2-azetizinone (10.0 g) in dry tetrahydrofuran (50 ml) was added at
the same temperature over 30 minutes to the mixture, the resulting
mixture was stirred for 15 hours. Thereafter, the solution was
concentrated until the amount was decreased to 50 ml, while the inner
temperature was kept at about 20° C. The unreacted zinc component
was separated by filtration. After the filtrate was diluted with toluene
(70 ml), water (30 ml) was added under cooling with ice, and a 1 N
aqueous solution of hydrochloric acid was further added to adjust pH at
4.0. The organic layer obtained by solution separation was washed with
water (15 ml) twice. While the inner temperature was kept at 20 to
30° C., the solvent was removed by distillation to obtain 30.0 g
of a toluene solution containing 15.5 g of
3-{(2R)-2-{(3S,4R)-3-[(1R)-1-tert-butyldimethylsilyloxy
ethyl]-2-oxoazetidin-4-yl}propionyl}-spiro[2,3-dihydro-4H-1,3-benzoxadine-
-2,1'-cyclohexan]-4-one.

[0075]After methanol (150 ml) was added for dissolution in the obtained
toluene solution, the solution was cooled to 0° C. Then, 30%
aqueous hydrogen peroxide (11.8 ml) and a 15% aqueous solution of sodium
hydroxide (15.3 g) were successively added to the solution. The mixture
was stirred at the same temperature for 1 hour and 40 minutes. Next,
after a 10% aqueous solution of sodium sulfite (145 g) was added dropwise
over 1 hour and 20 minutes, the mixture was stirred for 30 minutes. A 1 N
aqueous solution of hydrochloric acid was added to adjust pH at 9.6, and
methanol was removed by vacuum distillation. The precipitated crystal
component was separated by filtration and the crystal component was
washed with water (50 ml) twice. The filtrate and the washing solution
was mixed to obtain an aqueous alkaline solution containing 8.9 g of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid. The solution contained the 2S isomer in an amount
of 2.7% on the basis of the compound (I).

[0077]After ethyl acetate (75 ml) was added to the aqueous alkaline
solution containing 4.5 g of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid (compound (1)) obtained in Reference Example 2, 6N
HCl was added under cooling with ice to adjust pH at 2.9. After the
mixture was stirred for 10 minutes, an organic layer obtained by
separating a water layer was washed with water (15 ml) twice to obtain an
ethyl acetate solution containing 4.4 g of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propioni c acid. The solution contained the 2S isomer in an amount
of 2.7% on the basis of the compound (1).

Example 2

[0078]To the ethyl acetate solution of the compound (1) obtained in
Reference Example 3, toluene (150 ml) was added over 10 minutes. As a
result, a crystal was precipitated. The obtained slurry was concentrated
to 29.3 g, while the inner temperature was kept at 20 to 30° C.
The obtained slurry was cooled to -20° C. and stirred at the same
temperature for 2.5 hours. It was confirmed that the weight ratio of
toluene in the composition of the solvents at the moment was 1/2 or
higher. After the crystal was separated by filtration, the crystal was
washed with toluene (8 ml) twice. The obtained wet crystal was dried
under reduced pressure at room temperature for 24 hours to obtain 4.3 g
of a dry crystal of the compound (1).

[0079]Crystal purity: 98.7%

[0080]2S Isomer content: 0.8%

[0081]2S Isomer removal ratio: 70%

[0082]Crystal recovery ratio: 97.5%

Comparative Example 2

[0083]Concentrated hydrochloric acid was added to the aqueous alkaline
solution containing 4.4 g of the compound (1) obtained in Reference
Example 2 under cooling with ice to adjust pH at 3.0. As a result, a
crystal was precipitated. The obtained slurry was stirred for further 30
minutes under cooling with ice. The crystal was separated by filtration,
and washed with water (25 ml). The obtained wet crystal was dried under
reduced pressure at room temperature for 17 hours to obtain 4.7 g of a
crystalline solid of the compound (1), containing 4.3 g of pure compound.

[0089]After
(3S,4R)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1S)-1-methyl-2-p-
ropenyl]azetidin-2-one (10.0 g), acetic acid (16.1 g), ethyl acetate (100
ml) and water (70 ml) were mixed, and the mixture was stirred. While the
reaction solution temperature was kept at 6 to 15° C., potassium
permanganate (28.3 g) was added over 1.5 hours. The mixture was stirred
at 7° C. for 3 hours. Thereafter, a 27% aqueous solution of sodium
hydrogen sulfite (150 ml) was added, while the reaction solution
temperature was kept at 6 to 13° C. The mixture was stirred at
7° C. for 30 minutes, and 6N HCl was further added to adjust pH of
the reaction solution to be at 1.5. The mixture was stirred at 7°
C. for 30 minutes. An organic layer obtained by separating the mixture
was washed with water (50 ml) twice to obtain an ethyl acetate solution
containing 9.6 g of
(2R)-2-{(3S,4S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-oxoazetidi-
n-4-yl}propionic acid. The solution contained a 2S isomer in an amount of
1.3% on the basis of the compound (1).

Example 3

[0090]To the ethyl acetate solution containing 4.8 g of the compound (I)
obtained in Reference Example 4, toluene (150 ml) was added over 10
minutes. As a result, a crystal was precipitated. The obtained slurry was
concentrated to 32.0 g, while the inner temperature was kept at 20 to
30° C. The obtained slurry was cooled to -20° C. and
stirred at the same temperature for 2.5 hours. It was confirmed that the
weight ratio of toluene in the composition of the solvents at the moment
was 3/4 or higher. After the crystal was separated by filtration, the
crystal was washed with toluene (8 ml) twice, and the obtained wet
crystal was dried under reduced pressure at room temperature for 24 hours
to obtain 4.7 g of a dry crystal of the compound (1).

[0091]Crystal purity: 99.0%

[0092]2S Isomer content: 0.3%

[0093]2S Isomer removal ratio: 73%

[0094]Crystal recovery ratio: 97.5%

Example 4

[0095]The powder x-ray diffraction of the crystal obtained by the method
of Example 2 was measured by using the following apparatus under the
following measurement conditions.